Contributed by: Richard Kenney
The book makes it clear (but the movie does not) that Miriam Blaylock is not human. She is of another species which evolved as the perfect predator, who blend in with their prey (human kind). The book does a great job of weaving in vampire myths and explaining how they came to be. For example, when Miriam's species sleeps, they enter a comatose state and cannot wake for six hours (the deep sleep is why they don't age). At this time they are completely vulnerable to attack by humans. In Eastern Europe in the middle ages (Transylvania), when humankind began to realize that Miriam's species existed, Miriam's species was sometimes forced to sleep in cemeteries for protection, knowing that humans were too superstitious to enter them at night. When they would arise in the morning and leave the cemetery, humans who saw them would assume that they were undead and rising from the grave.
The book has a completely different ending. Miriam survives but Sarah does not and, in the last scene, Miriam is walking the streets of San Francisco, noting how comforting it is in the afternoon when she can travel under cover of fog.